Thermostat



Jgn. 30, 1934- D. MCK. GREER THERMOSTAT 2 Sheerls-Sheet 1 Filed March 51, 1953s 1 2. .1 11 r51- 2 TIL-T. a

INVENTOR. G, Mom; Mme/u ATTORNEY Du/vi) 9160.

Jan. 30, 1934. D. McK. GREER THERMOSTAT Filed March 31, 1933 2 Sheets-Sheet 2 INVENTOR. gym/av, 6

@momma BY 3 W ATTORNEY Patented Jan. 30, 1934 UNITED STAT-ES PATENT OFFICE THERMOSTAT David McKay Greer, Washington, D. 0., as-

signor to American Instrument Company, Washington, D. 0., a corporation of Delaware Application March 31, 1933. Serial No. 663,843 20 Claims. (01. 209-141) My invention relates broadly to thermoreguside of the operating reservoir than on the other lators and more particularly to a construction of side thereof for facilitating the discharge and readily adjustable thermoregulator which has no return of mercury to the capillary by a tipping setting constant. operation. One of the objects of my invention is to pro- Another object of my invention is to provide 60 vide a construction of settable thermoregulator a construction of thermoregulator having a gradof the mercury in glass type. uated scale on the capillary thereof measured Another object of my invention is to provide downward from a zero position adjacent the a construction of thermoregulator in which the electrode at the base of the operating reservoir.

effective quantity of mercury is readily adiust- Other and further objects of my invention re- 5 ble for insuring the operation of the thermoside in a construction of readily settable thermo regulator at a predetermined temperature, regulator having no setting constant as set forth A further object of my invention is to provide more fully in the specification hereinafter 01- a construction of thermoregulator wherein a l wi y r f rence to the accompanying drawstorage reservoir is provided adjacent the top ineswh rein: 7| of the capillary into which mercury may b Figure 1 is an elevational view of the thermoreadily discharged or from which mercury ma regulator of my invention; Fig. 2 is a central verbe drawn for regulating the quantit f mercury tical longitudinal sectional view taken through in the capillary and thereby predetermjning the a thermoregulator constructed in accordance operating temperature of the thermostat. with my invention; Fig. 3 is a horizontal cross 7! A still further object of my invention is to prosection taken on line 3-3 of Fig. 1; Fig. 4 is a vide a construction of thermoelectric regulator central vertical longitudinal section taken in which the capillary merges at its extremity through the operating and secondary reservoirs into an operating reservoir having an annular and showing on an enlarged scale the arrangesecondary reservoir around the periphery of the ment of the upper contact in the thermoregu- 80 operating reservoir adapted to receive or deliver lat-or; Fig. 5 shows a modified form of upper elecmercury to the operating reservoir for controlling trode for the thermoregulator of my improved the efiective length of the mercury column in the construction; Fig. 6 shows a further modified capillary. form of upper electrode and the arrangement Still another object of my invention is to prothereof within the head of the thermoregulator, 85 vide a construction of mercury in glass type of and also disclosing a modified formation of the thermoregulator including a capillary merging apex of the thermoregulator, to facilitate the reinto a substantially cup-shaped operating reserturn of mercury to the operating reservoir; Fig. '1 voir at its upper extremity, the said operating is a horizontal sectional view taken on lines 7-7 reservoir being surrounded by an annular secof Fig. 6; Fi 8 is a r l vertical longitudinal 9o ondary reservoir to receive mercury discharged section illustrating a further modified form of from the capillary or to provide surplus mercury electrical contact constructed in accordance with which may be delivered to the capilla f r my invention; Fig. 9 is a central vertical longitureadily setting the mercury column for condinal section through a modified form of controlling the precision operation of the thermosfirllction of Operating reservoir and Secondary 95 l t reservoir in which the secondary reservoir is ec- A further object of my invention is to provide centric with respect to the operating reservoir a construction of thermoregulator having a with a consequent larger volume for mercury on operating reservoir connected with the top of one d of the operating r serv r than on the the capillary and a secondary reservoir disposed other side thereof; Fig. 10 is a horizontal section 10 eccentrically with respect to the operating restaken on line 10-10 f F g. 9; Fig. 11 is a central ervoir for facilitating the discharge of mercury Vertical IOHgitudinal Section through fu ther I from the operating reservoir, or th return of modified construction of operating and secondmercury to the operating reservoir by a tippi ary reservoir, wherein the secondary reservoir is operation. entirely closed at one side for accommodating a A still further object of my invention is to volume of mercury at the other side of the provide a construction of operating reservoir. and opera ing r v i i 1 i a i ontal section secondary reservoir for'the upper end of a capiltaken on line 12-12 of Fig. 11; Fig. 13 is a thelary of a thermoregulator, wherein a larger voloretical view illustrating the manner of returnume is provided in the secondary reservoir on one ing mercury to the operating reservoir for subsequent return to the capillary; and Fig. 14 illustrates a modified form of establishing electrical connection with the mercury within the expansion bulb.

All thermoregulators of the mercury in glass type constructed prior to my invention operate on the principle of the mercury rising in a capillary and closing two adjacent electrical contacts.

In order to change the temperature at which the regulator makes contact, it is necessary that mercury be removed from the bulb of the regulator for higher temperature settings and that it be put back into the bulb for lower temperature settings. It has heretofore been proposed to draw the end of the capillary into a substantially closed terminus having a relatively narrow aperture at its extremity and terminating in a bulb at the top of the capillary. The adjustment of such a thermostat is extremely critical.

Considerable skill and practice is necessary before one becomes proficient in transferring exactly the right amount of mercury, which, for slight changes in temperature, is a very minute quantity. In order to force mercury out of the capillary, it is necessary that the bulb be heated to some temperature above that for which the regulator is set and this difference in temperature (sometimes called the regulator constant) depends upon the amount of storage space in the regulator above the upper contact. If this space is made small to facilitate setting of the regulator, there is the possibility that the regulator will lose its setting if overheated even slightly. If, on the the other hand, this storage space is made large to permit of considerable overheating without loss of setting, it is necessary that the regulator be heated to a high temperature before even one drop of mercury is transferred out of the capillary. As an example, suppose it is desired to have a regulator set for 98.6 F. and, at the same time, have an overflow capacity of 40 F. It is found upon test that the regulator is actually set for 98 F. and to raise the setting it is necessary to raise the temperature to the full overflow capacity of the regulator, plus the difference between 98 F. and 98.6 F. If the regulator has an overflow capacity of 40 F., its temperature must be raised to 98.6+ i0=138.6 F. to obtain the proper regulation at 98.6 F. In order to determine if the proper amount of mercury has been transferred, the regulator temperature must be low ered to 98.6" F. and a test made. Should the setting not be correct, it is necessary to again heat the regulator to the former temperature and transfer some more mercury either into or out of the capillary. This is necessarily a slow procedure and, in cases where the temperature must be frequently changed, this type of regulator even with its obvious other advantages is undesirable. The construction of my invention is designed to furnish a regulator with an overflow capacity of any reasonable quantity of mercury and. at the same time, induce the regulator constant to zero.

Referring to the drawings in detail, reference character 1 designates the main reservoir for the mercury of the mercury in glass regulator of my invention extending into the capillary 2 which terminates in the bulb 3 connected with the top of the capillary 2. The bulb 3 may be sealed to the capillary 2 so that the bore of capillary 2 is in precise alignment with the bore 4 extending upwardly into bulb 3. The bulb on the end of the capillary in a variety of ways such as blowing in such manner that the bore of the capillary 2 is contiguous with the bor 4 of the bulb. The bulb 3 has an operating reservoir 5 which may be disposed centrally thereof as shown in Figs. 1-8, or arranged eccentrically therein and connected with the bore 4, as shown in Figs. 9-13. In Figs. 1-8, the operating reservoir 5 is shown in the form of a cup-shaped member having a bowl-shaped portion and terminating in an upper annular lip 6 which is slightly rolled outwardly as represented at 60. The cupshaped member 5 is surrounded by a concentrically disposed secondary reservoir 7. The secondary reservoir 7 is arranged between the outside wall of cup-shaped member 5 and the inside wall of bulb 3. The secondary reservoir 7 may extend to a level which is either coincident with or which extends below or above the level of the bottom of the cup 5. In Figs. 1 and 2, I have shown the secondary reservoir 7 disposed on a level below the level of the central reservoir by a distance X. In Figs. 413, the level of the secondary reservoir has been represented above the level of the central reservoir by a distance X. In the form of the invention shown in Figs. 1-4, the upper electrode is represented by a conductor 9 which is sealed into the body of the bulb 3 and projects at 9a into the upper extremity of the bore 4 substantially at the lowermost level of the cup-shaped member 5. A flexible connection 10 extends to the conductor 9 for providing a circuit connection to the upper electrode in the thermoregulator.

In lieu of the arrangement of electrode 9 shown in Figs. 14, I may provide a sealed-in platinum disc 11 at the base of the cup-shaped member 5 as shown in Fig. 6. In this arrangement the platinum disc 11 is apertured at 11a in alignment with the bore 4 and has a connection 12 extending therefrom and passing through the bulb 3 as shown, to provide a terminal for the flexible wire connector 14 as shown. The mercury column 15 is free to rise in the capillary 2 and establish contact with the platinum disc 11 in the operating reservoir 5 and to flow through the aperture 11a into the cup-shaped reservoir 5.

In order to facilitate manufacture of the thermoregulator I may introduce the upper electrode in a different manner as shown in Fig. 5 wherein upper electrode 16, bent at a right angle 16a, projects downwardly as represented at 16b to a position centrally of bore 4 and directly adjacent the lowermost level of the bottom of the cupshaped member 5. In this arrangement the electrode 16 is sealed in the side wall of bulb 3 as represented at 3a. Electrical connection is established from the end of ductor 17.

Still another method of sealing the upper electrode in the thermoregulator has been illustrated in Fig. 8 wherein a wire element 18 is introduced through the sealing-off apex of bulb 3 as indicated at 19 and extends to a position 182) centrally of the bore 4 and directly adjacent the lowermost level of cup-shaped reservoir 5. The upper end of electrode 18 provides means for establishat 20 to one side of the thermoelectric regulator circuit. The other electrode for the thermoregulator passes through the side wall of the capillary 2 as represented at 21 or, as shown at Fig. 14 through the wall of the mercury expansion bulb generally at 25 for establishing connection with the mercury column 15. A connection 22 is taken to the contact 21 or a contact in the mercury expansion bulb for electrically connecting the thermoregulator in a control circuit. The

electrode 16 through con- 1 at a position indicated cup-shaped reservoir is the operating reservoir which receives mercury from the capillary 2 in the course of the normal expansion of the mercury column under conditions of rising 5 temperature. The annular reservoir 7 which surrounds the operating reservoir 5 has been termed the secondary reservoir. The mercury which rises in the operating reservoir 5 spills into the secondary reservoir 7, or surplus mercury from the capillary 2 may be discharged into the secondary reservoir by tipping the regulator. The operating reservoir 5 may be made with sufficient volume to hold the mercury expelled from --the capillary 2 by any practical overshoot in tem- 15 perature deemed desirable, such as a 40 or more overshoot.

It will be observed that I have specified the mounting of the upper electrode directly adjacent the lower level of the cup-shaped reservoir 5. I take into account the rounded surface of the mercury as it rises in the capillary in placing the location of the upper electrode so that elec trical contact occurs at the surface of the mercury immediately after all mercury has been spilled from the reservoir 5. In this way I avoid the introduction of a setting constant.

The arrangement of electrical connection in the wall of the mercury expansion bulb 1 avoids the weakening of the wall of the capillary and yet provides good electrical connection with the mercury through the wall of the mercury expansion reservoir, which is usually somewhat thicker and more capable of sustaining the tension which may be placed upon such electrical connection. In Fig. 1, I have illustrated a scale 26 which is graduated in degrees measured downward from the upper electrode 9a. This scale facilitates setting or checking of the setting of the regulator in the following manner. The expansion bulb of the regulator is immersed in a liquid at such temperature as to bring the top of the mercury column even with some point on the scale. If the temperature of the liquid in which the bulb is immersed is now determined by use of a thermometer, the setting of the regulator will be the sum of this temperature and the reading of the scale opposite the top of the mercury column.

In lieu of the concentric relation of the operating reservoir with respect to the secondary reservoir, I may employ an eccentric relationship for facilitating the movement of the mercury to and from the operating reservoir. Fig. 9 illustrates one form of eccentric arrangement. In Fig. 9 the operating reservoir 5 is connected to the upper extremity of capillary 2 in a concentric manner as before. However the secondary reservoir '7 has a smaller volume on the side 7a thereof than on the side '71) thereof in bulb 3. This arrangement is shown more clearly in Fig. 10. As illustrated in Figs. 11 and 12, the operating reservoir 5 may be wholly connected with one of the side Walls of bulb 2 as represented at 30, and shown more clearly in Fig. 12. Reservoir '7 is then wholly to the right of operating reservoir 5. Thus it will be seen that the annular secondary reservoir may have larger volume on one side than on the other, or it may be entirely closed on the smaller side. The advantage of this is that mercury may be discharged from the operating reservoir 5 by tipping the same in one direction, and restored to the operating reservoir by tipping in the opposite direction, as represented for example in Fig. 13. If the operating reservoir 5 is concentric with the secondary reservoir 7;. 7, a quick shake is necessary to return the mercury to the reservoir 5, which is however difiicult and tedious. Fig. 8 illustrates a construction of bulb for the thermostat which facilitates the return of the mercury from the secondary reservoir 7 to the operating reservoir 5. In this construction the upper extremity of the bulb 3 is depressed to provide an inverted apex as shown at 30. This may be accomplished after the thermostat has been completed and simply involves heating the tip of the bulb to a sufllcient extent to allow the inversion of the apex. This provides a downwardly directed cone-shaped wall directly above the center ofthe operating reservoir and serves as a guide against which mercury is directed upon a quick upward jerk of the thermostat for restoring the mercury in a path represented generally by the dotted arrows 31 into the operating reservoir. That is to say, mercury which is thrown upwardly by avertical jerk of the thermostat, is reversed in one direction of movement and directed into the operating reservoir and observations made until the required setting is obtained.

It will be observed that the laterally disposed reservoir arrangement may be brought about either by thickening the wall of the bulb 3 or.

one side, or disposing the outer bulb eccentric with respect to the operating reservoir 5. Thus it is possible to provide an eflicient method for returning the mercury from the secondary reservoir to the operating reservoir and then to the capillary as illustrated by the tipping operation in Fig. 13.

The operation of the thermoregulator is as follows: Mercury rises in the capillary as in the ordinary type of regulator until the regulator is at the desired operating temperature. If there is an excess of mercury in the capillary, the mercury is now in the upper cup or operating res ervoir 5 and may be spilled into the secondary reservoir 7 by tipping the regulator. If there is not enough mercuryin the regulator capillary 2 in the beginning, there will be a section at the top of the capillary 2 not filled with mercury. If the temperature is raised until the mercury fills the capillary 2 and the regulator is tipped until some of the mercury in the bulb is gathered into the cup 5, this latter mercury will join the former. If the regulator is cooled below the operating temperature, an excess of mercury will be drawn into the capillary 2 and it may be spilled out when the operating temperature is again reached.- Thus it may be observed that the regulator has ample storage capacity for all reasonable variation in' temperature and no setting constant.

From a consideration of the foregoing, it will be appreciated that the thermoregulator of my invention is readily settable. By tipping the regulator, mercury may be restored from the secondary reservoir '7 to the capillary 2 through the operating reservoir 5, as represented in Fig. 13. The construction of thermoregulator according to my invention provides for a high degree of precision in the operation of the instrument for temperaiure control, at the same time facilitating i adjustment to selected operating temperatures.

I have described my invention in certain preferred embodiments but I realize that modifications may be made by those skilled in the art and I intend no limitations upon my invention other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows: 1. A thermoregulator comprising a mercury in glass column, a bulb at the extremity of said col umn, an operating reservoir having a diameter greater than the diameter of said column and disposed wi'hin said bulb and connected with said column, a secondary reservoir concentrically dis posed between the inside wall of said bulb and the said operating reservoir, a lower electrode in said column. and an upper electrode intermediate the extremity of said column and the lowest level of said opcraling reservoir.

2. A thermoregulator comprising a capillary tube for mercury, a bulb at the upper extremity of said capillary tube, a cup-shaped reservoir having a diameter greater than the diameter of the bore of said capillary tube and disposed within said bulb and connected with the extremity of said capillary tube, and an annular reservoir surrounding said cup-shaped reservoir and immediately adjacent the inner wall of said bulb.

3. A thermoregulator comprising a capillary for mercury, a body of mercury in said capillary, a bulb at the upper extremity of said capillary, a cup-shaped reservoir having a cross sectional area reater than the cross sectional area of said capillary disposed centrally of said bulb and connected at its lowest extremity with said capillary, a secondary reservoir surrounding said cup-shaped reservoir, an electrode in said capillary, and an electrode adjacent the bottom of said cup-shaped reservoir.

4. A thermoregulator comprising a capillary for mercury. a body of mercury in said capillary, a bulb at the upper extremity of said capillary, a cup-shaped reservoir having a cross sectional area creator than the cross sectional area of said capillary disposed cenlrally of said bulb and connected at its lower extremity with said capillary, a secondary reservoir surrounding said cup-shaped reservoir, said secondary reservoir teminating in a level above the level of said cup-shaped rcservoir, an electrode in said capillary, and an electrode adjacent the lowest level of said cup-shaped reservoir in the path of said capillary.

5. A thermoregulator comprising a capillary, a mercury column in said capillary, a bulb connected with the upper extremity of said capillary, a cupshaped member having a cross sectional area greater than the cross sectional area of said capillary and having its lower portion connected with said capillary, an opening at its upper portion into said bulb, a secondary reservoir disposed between the exterior wall of said cup-shaped member and the interior wall of said bulb and terminating above the lowest level of said cup shaped member, an electrode in said capillary, and an electrode adjacent the lowest level of said cup-shaped member in the path of said capillary.

6. A thermoregulator comprising a capillary, a bulb connected with the upper extremity of said capillary, a cup-shaped member in said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected at its lower extremity with said capillary,

, the upper end of said cup-shaped member having outwardly flared walls extending into said bulb, a secondary reservoir disposed between the outside wall of said cup-shaped member and the interior wall of said bulb, said secondary reservoir terminating in a level above the lowest level of said cup-shaped member, an electrode in said capillary adjacent the lowest level of said cupshaped-member, and another electrode in said capillary in a position below the aforementioned electrode.

'7. A thermoregulator comprising a capillary, a body of mercury in said capillary, a bulb on the end of said capillary, an operating reservoir within said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected with said capillary for receiving mercury from said capillary, and a storage reservoir in said bulb for receiving mercury from the operating reservoir, said storage reservoir being adapted to restore mercury to said operating reservoir upon tipping of said capillary for in turn restoring mercury to said capillary.

8. A thermoregulator comprising a capillary, a body of mercury in said capillary, a bulb on the end of said capillary, an operating reservoir within said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected with said capillary for receiving mercury from said capillary, a storage reservoir in said bulb for receiving mercury from the operating reservoir, said storage reservoir being adapted to restore mercury to said operating reservoir upon tipping of said capillary for in turn restoring mercury to said capillary, an electrode in said capillary, and another electrode intermediate the end of said capillary and the bottom of said operating reservoir.

9. A thermoregulator body of mercury in said end of said capillary, an operating reservoir within said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected with said capillary for receiving mercury from said capillary, a storage reservoir in said bulb for receiving mercury from the operating reservoir, said storage reservoir being adapted to restore mercury to said operating reservoir upon tipping of said capillary for in turn restoring mercury to said capillary, an electrode extending through the side wall of said bulb and bent at an angle and terminating in a position adjacent the lowest level of said operating reservoir and in alignment with said capillary, and another electrode connected with said capillary at a point from the aforementioned electrode.

10. A thermoregulator comprising a capillary, a body of mercuiy in said capillary, a bulb on the end of said capillary, an operating reservoir within said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected with said capillary for receiving mercury from said capillary, a storage reservoir in said bulb for receiving mercury from the operating reservoir, said storage reservoir being adapted to restore mercury to said operating reservoir upon tipping of said capillary for in turn restoring mercury to said capillary, an electrode extending through the end of said bulb in direct alignment with said capillary and terminating at the lowest level of said cup-shaped member and adjacent the extremity of said capillary, and another electrode remote from the aforesaid electrode.

11. A thermoregulator comprising a capillary, a body of mercury in said capillary, a bulb on the end of said capillary, an operating reservoir within said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected with said capillary for receiving mercury from said capillary, a storage reservoir in said bulb for receiving mercury from the operating reservoir, said storage reservoir being adapted to restore mercury to said operating reservoir upon tipping of said capillary for in turn restoring mercury tosaid capillary, a ring shaped eleccomprising a capillary, a capillary, a bulb on the trode disposed adjacent the lowest level of said operating reservoir and at the extremity of said capillary, said ring shaped electrode providing a conductive passage for mercury from said capillary into said operating reservoir, and another electrode in said capillary remote from the aforesaid electrode.

12. A thermoregulator comprising a capillary for mercury, a bulb at the upper extremity of said capillary and an operating reservoir disposed within said bulb having a cross sectional area greater than the cross sectional area of said capillary and connected with said capillary, said operating reservoir being disposed eccentrically with respect to said bulb.

13. In a thermoregulator, a capillary tube for mercury, an operating reservoir having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the extremity of said capillary tube, and a bulb connected with said capillary tube and surrounding said operating reservoir, said bulb being disposed eccentrically with respect to said operating reser- 14. In a thermoregulator, a capillary tube for mercury. an operating reservoir having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the extremity of said capillary tube, a bulb connected with said capillary tube and surrounding said operating reservoir, an annular reservoir formed between the walls of said bulb and the walls of said operating reservoir, said annular reservoir having a larger volume on one side than on the other side of said operating reservoir.

15. A thermostat comprising a capillary tube for mercury, a bulb connected with the upper end of said capillary, an operating reservoir having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the upper extremity of said capillary tube, one wall of said operating reservoir being united with the wall of said bulb on one side thereof and being spaced from the wall of said reservoir on the other side thereof for forming a secondary reservoir extending partially around said operating reservoir.

16. A thermoregulator comprising a capillary tube for mercury, a bulb connected with the upper end of said capillary tube, an operating reservoir having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the upper extremity of said capillary and providing a circular container for mercury and a substantially crescent shaped secondary container for mercury within said bulb and extendng partially around said operating reser- 17. A thermostat comprising a capillary tube for mercury, a bulb at the top of said capillary tube, a cup-shaped member having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the extremity of said capillary tube and disposed within said bulb, a secondary reservoir adjacent said cupshaped member in said bulb, and a depression formed in said bulb directly over said cup-shaped member.

18. A thermostat comprising a capillary tube for mercury, a bulb connected with the top of said tube, an operating reservoir having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the extremity of said capillary tube and disposed centrally of said bulb, a secondary reservoir disposed between said operating reservoir and the interior walls of said bulb, the upper portion of said bulb being directed downwardly for forming a guide for facilitating the restoring of mercury from said secondary reservoir to said operating reservoir.

19. A thermostat comprising a capillary tube for mercury, a bulb at the top of said capillary tube, an operating reservoir within said bulb having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the extremity of said capillary tube, a secondary reservoir adjacent said operating reservoir and an inwardly directed apex on said bulb disposed centrally over said operating reservoir for facilitating the restoring of mercury from said secondary reservoir to said operating reservoir.

20. A thermostat comprising a capillary tube for mercury, a bulb at the top of the capillary tube, an operating reservoir having a cross sectional area greater than the cross sectional area of said capillary tube and connected with the upper extremity of said capillary tube and concentrically disposed within said bulb, an annular secondary reservoir surrounding said operating reservoir within said bulb, and an inverted apex on said bulb directed toward said operating reservoir for facilitating the restoring of mercury from said annular secondary reservoir to said operating reservoir.

DAVID McKAY GREER. 

